In Armstrong County, the plan is to open mail ballots and flatten them out in a workroom behind Ms. Kuznik’s office. Workers escorted by sheriff’s deputies will carry the ballots to the public works garage, where the county keeps its scanners

Yet in an increasingly polarized country, that center may be shifting.

What’s perhaps most significant about the early vote, though, is that a group of new African-American voters have been energized: of the Black voters in Florida who’ve already voted, about 15 percent of them did not cast ballots in 2016 or 2018.

For example, Atlas misrepresented the effectiveness of masks, suggested that lockdowns kill people and discouraged testing of asymptomatic people.

He also dismissed forecasts from the Institute for Health Metrics and Evaluation at the University of Washington School of Medicine that forecasts 399,000 coronavirus deaths in the US by February 1 under current conditions.

In October, Twitter removed a tweet from Atlas that sought to undermine the importance of wearing a face mask, because Atlas' tweet was in violation of the its Covid-19 Misleading Information Policy, a spokesman for the company told CNN. The tweet said, "Masks work? NO" followed by a series of falsehoods about the science behind the effectiveness of masks in combating the pandemic.

Mr. Biden, now the Democratic presidential nominee, has had his own misadventures with misstatements, caught on several occasions during his career in politics puffing up his own record. His first presidential campaign blew up in 1987 after he lifted lines from another politician’s speech without credit, overstated his academic accomplishments and was revealed to have been accused of plagiarism in law school. Mr. Biden, unlike Mr. Trump, admitted the errors, while calling them innocent mistakes. Still, he has been prone to exaggeration since then as well.

In late February, there were just a few dozen known cases in the United States, most of them linked to travel. But by summer, the virus had torn through every state, infecting more people than the combined populations of Connecticut and Oklahoma. And in the fall, the national death toll exceeded 230,000, more than the population of Boise, Idaho.

American life has been fundamentally reordered because of the virus. Concerts, parades and high school football games continue to be called off. Countless people have found themselves jobless and struggling to afford housing. Many schools and colleges have held few or no in-person classes this fall. More than 214,000 cases have been linked to colleges and universities over the course of the pandemic. Thousands more cases have been identified in elementary, middle and high schools.

The Times’s data collection for this page is based on reports from state and local health agencies, a process that is unchanged by the Trump administration's requirement that hospitals bypass the Centers for Disease Control and Prevention and send all patient information to a central database in Washington.

The Northeast experienced the worst this spring, as temporary morgues were deployed in New York City. Over the summer, cases spiked across the Sun Belt, prompting many states to tighten restrictions just weeks after reopening. By fall, the virus was filling rural hospitals in the Midwest and West as it devastated communities that had for months avoided the pandemic’s worst.

In Cook County, Ill., which includes Chicago, more than 5,400 people have died. In Los Angeles County, Calif., more than 300,000 people have had the virus, more than in most states. And in New York City, about one of every 352 residents has died.

Coronavirus cases have been reported in more than 23,000 nursing homes and other long-term care facilities, according to data collected by The New York Times from states, counties, the federal government and facilities themselves. More than 581,000 residents and employees of those homes have been infected, and more than 87,000 have died. That means more than 35 percent of deaths from the virus in the United States have been tied to nursing homes and other long-term care facilities.

In July, the Centers for Disease Control and Prevention reported more than 16,000 infections and 86 deaths tied to meat and poultry processing. But those numbers are almost certainly an undercount. Only 28 states provided data to the C.D.C., and many states and food processing companies have refused to provide case totals. Other large outbreaks have emerged on farms, in fruit or vegetable processing facilities and at plants where pet food is made.

Many police officials and extremism experts said that they were more worried about the period after Nov. 3, especially if no clear winner emerges.

In Chicago, days off have been canceled and officers notified that their shifts might extend to 12 hours.

National Guard units were also being called out in various states, including New Jersey, Wisconsin and Texas. Officials in the first two said the dearth of poll-station volunteers amid the pandemic meant a few hundred troops in civilian clothing would be needed to help count absentee ballots and other poll activities.

Florida is Florida. If Mr. Biden’s up eight or nine nationally, you’d sure think he’d figure out how to scratch out a narrow win in Florida … right? Maybe not. The final polls still show a tight race in the perpetually competitive state, and we have a bit of a split decision in the final polling today: NYT/Siena shows Mr. Biden up by three, ABC/Post shows Mr. Trump up by two, and St. Pete Polls (the rare robopoll that really tries to do a good job) shows Mr. Biden up by a point.

Miami-Dade County, Fla. A Democratic stronghold, it is not a county Mr. Trump would hope to win. But this majority-Hispanic county was a disappointment for Democrats in 2018, especially in heavily Cuban-American precincts. Younger Cuban voters have started identifying as Trump Republican here

Pinellas County, Fla. Perhaps the biggest swing county in the state, which backed Mr. Trump after twice backing Barack Obama, it is a Florida microcosm: solid Democrats in St. Petersburg and Midwestern retirees elsewhere.

Let’s look at some critical counties in North Carolina. The state has cities with large communities of Black voters, moderate professionals and college students and also big stretches that are more rural, whiter and conservative.

The prize will likely go to the candidate most popular among the Lumbee Indians, the county’s largest group. Mr. Trump held a rally here in October, and both campaigns pledged to support the tribe’s quest for federal recognition.

Let’s move on to Pennsylvania, which has two huge Democratic cities, big swaths of formerly Republican suburbs and a deeply conservative rural middle. This year’s election may hinge on this state, one of three that Mr. Trump won by less than one percentage point in 2016.

Michigan, historically Democratic, provided one of Mr. Trump’s most surprising victories in 2016. He won the state by 0.3 points.

Dane County, Wis. This is home to the University of Wisconsin-Madison, and it’s where Democrats surged in an April 2020 race for the State Supreme Court. Nearly as many votes were cast here as in Milwaukee County, even though Dane has less than 60 percent of Milwaukee’s population. Heavy turnout in early voting suggests Mr. Biden is claiming those votes.

President Donald Trump tweeted a video of the bus incident with the words "I LOVE TEXAS!" on Saturday, and claimed at a campaign rally on Sunday that his supporters were "protecting" the bus.

Many of the those who said they did not vote in 2016 said they had already voted this year. In Florida and Arizona, more than two thirds of nonvoters in 2016 who were identified as likely voters this year said that they had already cast a ballot. That figure was 56 percent in Wisconsin and 36 percent in Pennsylvania.

Based on the poll, however, it seems that Mr. Biden rather than Mr. Trump could be the beneficiary of record-busting turnout.

If the president is defeated, the most obvious explanation may be his weakness with women. Mr. Biden led Mr. Trump by double digits among female voters in each of the four states, and in some states the advantage was so significant that it offset Mr. Trump’s strength among men.

In a statement on Twitter on Saturday, Mr. Hollins said drive-through voting “is a safe, secure and convenient way to vote. Texas Election Code allows it, the Secretary of State approved it, and 127,000 voters from all walks of life have used it.”

“My message is simple: Pennsylvania is critical in this election,” Mr. Biden said at a “Souls to the Polls” event at Sharon Baptist Church on Sunday afternoon.

“Every single vote matters,” he added, noting that President Trump had only won the state in 2016 by roughly 44,000 votes. “The power to change this country is literally in your hands.”

“We need to get every soul in Philadelphia to the polls,” he said, urging voters to get their absentee ballots to a drop box “as soon as you can” if they still had one or to vote in person on Election Day. Mr. Biden will also hold a drive-in rally in Philadelphia on Sunday evening.

Cases from North Carolina and Pennsylvania are pending before the court, the latter a second attempt after a 4-to-4 deadlock last week. Justice Amy Coney Barrett, who was confirmed and sworn in to the Supreme Court on Monday night, could cast the decisive vote in that case

“That extension of Wisconsin’s ballot-receipt deadline ensured that Covid-related delays in the delivery and processing of mail ballots would not disenfranchise citizens fearful of voting in person,” Justice Kagan wrote. “Because of the court’s ruling, state officials counted 80,000 ballots — about 5 percent of the total cast — that were postmarked by Election Day but would have been discarded for arriving a few days later.”

And one of the most pivotal moments of her presidential campaign was on a debate stage: She declared “that little girl was me” as she questioned Mr. Biden’s opposition to busing. Even “Saturday Night Live” poked fun at Ms. Harris for her ability to craft a television-ready viral moment.

When it comes to the virus, the United States has come to resemble not the wealthy and powerful countries to which it is often compared but instead far poorer countries, like Brazil, Peru and South Africa, or those with large migrant populations, like Bahrain and Oman.

The second major theme is one that public health experts often find uncomfortable to discuss because many try to steer clear of partisan politics. But many agree that the poor results in the United States stem in substantial measure from the performance of the Trump administration.

President Trump has said the virus was not serious; predicted it would disappear; spent weeks questioning the need for masks; encouraged states to reopen even with large and growing caseloads; and promoted medical disinformation.

President Trump returned to the White House on Monday night, staging a defiant, made-for-television moment in which he ripped off his face mask and then urged the nation to put aside the risks of the deadly coronavirus that has swept through his own staff and sent him to the hospital for three days.

Trump climbed into a hermetically sealed, armored Chevy Suburban with at least two Secret Service agents so the president could wave to supporters outside Walter Reed National Military Medical Center in Bethesda, Md., where he was hospitalized from Friday to Monday.

Medical experts said the move put agents at risk.

Before the debate, Mr. Wallace had said that, if successful, his job was to be “as invisible as possible.” He sometimes managed to recede, though at other times he was caught up in the shout-fest. Rarely did he exert control over the chaos. “If you want to switch seats?” he offered gamely at one point to Mr. Trump.

Eventually, after Mr. Biden suggested he condemn the Proud Boys, a far-right organization widely condemned as a hate group, Mr. Trump declared, “Proud Boys: Stand back and stand by.”

Representative Ro Khanna, Democrat of California, said: “The problem is not that Trump refused to condemn white supremacy. It’s much worse. It’s that he acknowledged he was their leader by telling them to ‘Stand by.’”

Mr. Biden’s delivery was not always forceful. He did occasionally lose his cool and succumb to Mr. Trump’s barrage of taunts. But he mostly emerged unscathed, and for most Democrats, anything but a loss was welcomed as a clear win.

He didn’t match Mr. Trump’s volume. He often lost control of their exchanges. And the cross talk mostly kept him from building the emotional pitches to the audience that he relies on.

But it was also a clear, dismal and deafening reminder of what kind of country we actually do live in.

Mr. Trump himself has provided no evidence to back up his assertions, apart from citing a handful of Pennsylvania ballots discarded in a dumpster — and immediately tracked down, and counted, by election officials.

Meanwhile, the Department of Homeland Security and the F.B.I. have been issuing warnings, as recently as 24 hours before the debate, about the dangers of disinformation in what could be a tumultuous time after the election.

Indeed, his financial condition when he announced his run for president in 2015 lends some credence to the notion that his long-shot campaign was at least in part a gambit to reanimate the marketability of his name.